[swift-evolution] [Proposal] Adjusting `inout` Declarations for Type Decoration

[Trent Nadeau]

+1

I would also like to change the call site to use inout as well.

foo(inout myVariable)

On Fri, Jan 29, 2016 at 2:40 PM, Dave via swift-evolution <
swift-evolution at swift.org> wrote:

> +1
>
> On Jan 29, 2016, at 11:37, Erica Sadun via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> https://github.com/apple/swift-evolution/pull/127
>
> Adjusting inout Declarations for Type Decoration
>
>    - Proposal: TBD
>    - Author(s): Joe Groff <https://github.com/jckarter>, Erica Sadun
>    <http://github.com/erica>
>    - Status: TBD
>    - Review manager: TBD
>
> Introduction
>
> The inout keyword indicates copy-in/copy-out argument behavior. In its
> current implementation
> the keyword prepands argument names. We propose to move the inout keyword
> to the right
> side of the colon to decorate the type instead of the parameter label.
>
> *The initial Swift-Evolution discussion of this topic took place in the
> “Replace ‘inout’ with &” thread.*
> Motivation
>
> In Swift 2, the inout parameter lives on the label side rather than the
> type side of the colon
> although the keyword isn’t modifying the label but its type. Decorating
> types instead of labels offers identifiable advantages:
>
>    - It enables the inout keyword to properly integrate into full type
>    syntax, for example:
>
>    (x: inout T) -> U // => (inout T) -> U
>
>    - It avoids notational similarity with arguments labeled inout, for
>    example:
>
>    func foo(inOut x: T) // foo(inOut:), type (T) -> Void
>    func foo(inout x: T) // foo(_:), type (inout T) -> Void
>
>    - It better matches similar patterns in other languages such as
>    borrowing in Rust, that may be later introduced back to Swift
>
> Detailed design
>
> parameter → external-parameter-name optlocal-parameter-name : type-annotationtype-annotation → inout type-annotation
>
> Alternatives Considered
>
> Decorations using @inout (either @inout(T) or @inout T) were considered
> and discarded
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>
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>


-- 
Trent Nadeau
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